Telephone system



Oct. 11, 1938. A. G. LANG El AL TELEPHONE SYSTEM Filed March 16, 1937 5 Sheets-Sheet l m ut INVENTORS. A. G.LANG

'7TH.NEELV ATTORNEY Oct. 11, 1938. A. G. LANG ET AL 2,132,857

' TELEPHONE SYSTEM Filed March 16, 1937 3 Sheets-Sheet 2 .AGLLANG WVEN-TORSTHNEELV ATTORNEY Oct. 11; 1938. A. G. LAN ET AL 2,132,857

TELEPHONE SYSTEM Filed March 16, 1937 5 Sheets-Sheet 3 MARE/MAL E. 6. FIGS. 20 3 (1.5. PAT/653709 LOOP DIAL/N6 TRUNK T0 AUTOMATIC EXCHANGE PHI- rroR/wsy 1 Patented Oct. 11, 1938 TELEPHONE SYSTEM Albert G. Lang, Whitestone, and Thomas H. Neely, StewartManor, N. Y., assignors to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application March 16,

3 Claims.

This invention relates to telephone systems and more particularly to semiautomatic telephone systems.

An object of the invention is to facilitate the completion of calls through a toll switchboard to subscribers lines in an automatic community (unattended) exchange over operators connecting ,(cord) circuits primarily arranged for completing calls over trunk circuits to subscribers lines in main automatic exchanges at which exchanges a reversal of the line battery occurs when the final selector switch connects with the called line.

In toll switchboard cord circuits adapted for use with trunks of the above-described latter type, the dial circuit, once it is connected to the cord circuit, remains associated therewith until the before-mentioned reversal occurs at which time a polarized relay operates in the toll operators V io position to disconnect the dial circuit from the cord.

The circuits of what are commonly known as community dial ofiices, i. e. relatively small unattended satellite offices, are in some cases not arranged to transmit a battery reversal when the switch connects with the called line and hence a toll cord arranged to function with trunks to a main exchange over which a reversal occurs when the called line is seized could not be operated in t the same manner when connected to a community ofiice trunk for the reason that once the cord is connected to the trunk, the dial is connected and the speech transmission circuit through the cord is opened, all'under control of a polarized relay in $5 the position circuit which only operates when the line battery is reversed.

To overcome this diificulty, in the past, it has been the custom, when community office trunks are present in the same switchboard with trunks 4.0 to main exchange, to provide a special dial jack for each community ofiice trunk and, when a call is to be extended thereover, after plugging up the main trunk jack with the cord circuit to be used in completing the connection, to plug another cord circuit, from that over which the connection 7 is tobebompleted, into the dial jack. The operator then operates the dial key and actuates the dial now associated with this other cord and upon the completion of dialing removes this other cord 'from the dial jack whereupon a talking connection is established by means of the first cord. By this sequence of operation, the operator is enabled to complete calls over both types of trunks, but, in the case of connections to community ofiice 7 ytrunks, the double handling of cords consumes 1937, Serial Nb. 131,144 (01. 179-27) time and tends to slow up the service, particularly when a considerable number of such calls are completed at certain hours of the day.

A specific object of the invention is therefore to provide facilities whereby a single cord circuit can be interchangeably used to complete calls to trunks of either of the above described types without any of the objections above described.

A feature of the invention whereby the foregoing specific object is obtained, resides in such modifications of the present operators cord and position circuits and community ofilce trunks that upon completion of dialing on a community office trunk, and the release of a. positional dial key, the trunk conductors at the toll oflice will be reversed to supply line battery to the cord in a reversed direction thereby operating a polarized relay in the position dial circuit to disconnect the dial circuit from the cord and condition the cord circuit for conversation in the'same manner as when the call is extended to a main exchange and a line battery reversal automatically occurs thereat when the called line is seized.

Other features will appear hereinafter from the following description and accompanying drawings, Figs. 1, 2 and 3, which figures, when arranged as shown in Fig. 4, represent a toll operators cord circuit together with its associated position and dial circuit (as shown in Figs. 1

and 2) adapted to be connected to either a standard trunk circuit terminating at an automatic central office, arranged to reverse the battery supply to the cord when a called line is seized, or tobe connected to, a trunk circuit extending to a so-called community dial office not so arranged, as shown in Fig. 3. Fig. 1 of the drawings shows the position dial circuit. Fig. '2 shows a cord circuit with the operators telephone circuit, and Fig. 3 shows the outgoingjack of a standard out-dial trunk to an automatic exchange and the circuit at the outgoing end of a trunk to a community dial office arranged to simulate a battery reversal back into a connected dial circuit when the position dial keyis released at the termination of the dialing operation. V

A description of the operation of thecircuits of this invention follows:

Assuming that the operator is what is known as an inward operator and has answered a call by inserting the rear plug of her cord circuit C, Fig. 2, into a calling toll line, not shown, and desires to extend the connection to a station in an automatic ofiice reachedover trunk l0, she will first operate'the trunk dial key I thereby operating relay 2 in a circuit which can be traced from ground, contacts 3 or key I, contacts 4 of relay 5, contacts 6 of key i and winding of relay 2 to battery. RelayZ in operating connects battery to leads l1; 52, etc., to operate dial relays, such as l2, individual to the respective cords in the posi tion, when the front plug 9 of the cord is connected to an out-dial trunk such as H].

Trunk I is a standard out-dial trunk oi the type fully described in Patent 1,653,789 to Stokely dated December 1927 and shown in Figs. 2 and 3 thereof and therefore will not be redescribed here. v

By referring to the above patent it will be noted that the ring conductor of the trunk jack 2% shown in Fig. 2 is grounded through the lefthand winding of relay 262 and consequently when the plug 9 of the present cord is insertedin jack H, which corresponds to jack 296 of the Stokely patent, a circuit is completed to operate the dial relay i2 which can be traced from battery, contacts Q3 of relay 2, lead 1'1, upper winding of relay l2, contacts i l of relay [5, and the ring conductor of the plug 9 and jack H to ground in the trunk circuit as previously mentioned.

Dial relay l2 operates in this circuit, disconnectsrelay 33 from the plug sleeve, and at its contacts l6 completes a holding circuit for itself, including its lower winding, which can be traced from battery, contacts of polarized relay l1, relays !8 and IQ, lead 29, lower Winding and contacts E6 of relay l2, sleeve conductors of plug 9 and'jack H to ground over the left-hand contacts of relay 202 and the right-hand winding of relay 283 shown in the above-noted Stokely patent. Qperation of relay l2 also connects, at its contacts 29 and 36, the tip and ring conductors of the trunk to leads 3i and 32 extending to the dial circuit of Fig. 3.

Relay i8 is marginal and does not operate in the above traced circuit but relay l9 and trunk relay 263 do operate which latter relay, it will be observed, operates relay 2E3] to extend the trunk to pulsing relay 2M thereby connecting ground and battery respectively to the tip and ring conductors of the connected cord plug 9.

Relay ill in operating causes thesuccessive operation of relays 2i and 5, The latter relay locks up over its contacts 22 to ground on the dial key 1, opens the operating circuit of relay 2 and at its contact 23 closes a circuit from the dial 2G over lead 3i and contacts 29 of relay E2 to the tip conductor of the cord plug 9. When relay, 2 releases it disconnects battery from lead 71 and all other corresponding leads to other cords thereby openoperating, however, to permit relays 2m and 262 V in the trunk to lockup before the original operating circuit for relay 292 is opened by the release 7 of relay 2. Release of relay'Z closes, at its contact 25, a circuit to light the dial pilot lamp 25 which can be traced from battery, contacts 25 of relay 2, contacts 270f relay 2%, lamp 28 andcontacts 22 of relay to ground over contacts 3 of dial key I.

The circuit is now inrcondition for dialing and actuation of the dial 2% transmits pulses over the trunk to operate the pulsing relay 266 in the trunk as shown in Patent 1,653,789. As described in the above patent, when the connector switch in the distant oflice comes to rest onthe'called this circuit.

line, if the line is idle, current flowing back over the trunk to the dial circuit is reversed thereby causing polarized relay I! to operate. Operation of this relay opens the circuit including relays it, ill and I2 thus permitting relays i9 and i2 to release.

Relay 52 in releasing disconnects the trunk from leads 3! and 32 extending into the dial circult, opens contacts l5, and closes contacts 3d and 35. Closure of contacts 34 connects the tip of plug 5 through to the upper armature of relay I I5 anclclosure of contacts 35 connects'sleeve relay 33 to the plug sleeve whereupon relay 83 operates to ground over the sleeve of the trunk. Relay 33 in operating closes an obvious circuit to operate relay l5 which relay closes its inner upper and lower contacts to connect the tip and ring of plug 9 through to the cord.

Release of relay l9 releases relay 2| and if the operator released dial key 8 at the conclusion of the dialing operation, relay 5 will new release thereby extinguishing lamp 26 which completely restores the dial circuit to normal and conditions the cord for conversation.

Call to a community dialomce In case the called subscriber is reached over a trunk to a so-called community dial office'which is not arranged to send a current reversal back to operate polarized relay I? to release the dial circuit from the cord when the called subscribers line is reached, some means must be provided to simulate such a reversal in order to free the dial circuit and condition the cord for conversation and to accomplish this the trunk T (Fig. 3) has beenprovided, the operation of which is as follows: I I

When the operator desires to reach a community dial office subscriber, she first operates dial key l as before described, thereby operating relay 2 which connects battery over leadsli, l2, etc. to operate the respective dial relays such as l2 when the respective plug, such as 9, is inserted'in trunk jack 3% at which time a circuit is completed to operate relay 12 which can be traced from battery, contacts l3 of relay 2, lead '11, upper winding of relay 52, contacts id of relay 15, ring conductors of plug 9 and jack 36, contacts 3? of relay 38, contacts 39 of relay 30 and lower winding of relay 6! to ground. Relays l2 and ii operate in Operation of relay 12 extends the tip and ring of the plug 9 to the dial circuit (Fig. 1) over its contacts 29 and 39 and leads]?! and 32, and prepares a locking circuit for itself at contacts it. Relay 4! in operating operates relay 42 r in a circuit which can be traced from battery, contacts of polarizedrelay ll of the dial circuit,

windings of relays l8, l9 and the locking winding and contacts lb of relay l2, sleeve of the plug 9 and jack 3%, contact 43 of. relay 4! and lower winding of relay 42 to ground.

In the standard out-dial trunk IE, beforediscussed and described in Patent 1,653,789, the right-hand winding of sleeve relay 293 is of sufliciently'high resistance to prevent operation of marginal relay l8 in the dial circuit, but the lower winding of sleeve relay A2 in the community trunk T (Fig. 3 or the present application) is made low' enough to permit this relay (A) to operatethereby closing a circuit to operate relay '15 which can be traced from battery, winding of relay 15, contacts of relay l8 and the upper normal contacts of the dial to ground. Operation of relay 15 opens at its contact 76 the normal short-circuit around resistance 17 and closes its contact 18 thereby transferring the lead 19, which extends' to ground through the transformer winding 80 of the operators induction coil in the telephone circuit OT, shown at the bottom of Fig. 2, from the lead 8| normally connected to the tip of the plug 9, to the lead 32 and thence to the ring conductor of the trunk in order to receive dial tone from the distant'community office 'over the ring conductor of the trunkh Relay l9 also operates in this circuit, as previously described, which operates relays 2| and in turn. Relay 5 releases relay 2 which completes the circuit of dial pilot lamp 26'. Relay 5 in operating also closes its contacts 23 which extends lead 3| to the dial 24. With relay I2 operated and locked when relay 5, which is slow to operate, finally closes its contacts dial 24 is con nected across the tip and ring springs of the trunk jack 36 in series with polarized relay I1. Operation of trunk relay 42 -completes, at its lower contacts an obvious circuit to energizerelay. 40, which circuit was prepared by the operation of relay 4|, and a second obvious and parallelcircuit to operate slow acting relay -44.

Relay 49 in operating completes a'locking circuit for relay 4| which can be traced from ground, contacts 41 of relay 49', contacts 48 of relay 38, and contacts 49 and upper winding of relay4| to battery. Relay 46 also opens its contacts 39 and closes contacts 59 thereby transferring the connection of the ring conductor of the jack 36 from the lower or operating winding of relay 4| to the lower winding of relay 5|, which latter relay now operates. Further, relay 49 opensits lowermost contact thereby disconnecting battery from'the lower or primary winding of relay 38 and preventing that relay from falsely operating in response to the operation of relay 45 which immediately follows. When relay 44, closes its contacts it completes a circuit for relay 45 whichis slow acting. After a short interval this latter relay operates and in turn operates relay 46. Relay 45 is 3 made slow to operate in order to insure that relay 40 has operated and removed battery from relay 38 before relay 45 closes its lowermost contact which otherwise would cause the premature operation of that relay (38) which is not desired at this time.

Relay 45 in operating closes, at its contact 52, an obvious circuit for operating relay I I3 and at its contact 53 closes an equally obvious circuit for operatingrelay 54. Operation of relay I I3 connects ground through resistance 55 to the righthand terminal of the upper winding of pulsing relay 5?. Operation of relay 54'closes its contact 93 thereby connecting battery through the'lower winding of relay 5? and thence to the left-hand armature of relay 5 in the dial circuit (Fig. 1) which due to its slow-acting characteristic has not yet operated. This circuit can be traced from battery, contact'53 of relay 54, leads 64 and 165,

operates almost immediately after relay 54 and the foregoing circuit may be continued over contact 23 of relay 5, pulsing contact82 of dial24, resistance 11, winding of polarized relay I1, lead 32, contact 35 of relay l2, contact l4 oi=relay l5,

ring conductor of plug 9 and ring spring of jack 35, contact 31 of relay 38, contact 59 of relay 40 to ground through the lower winding of relay. 5|.

, the original condition which existed before The resistance of this circuit, due to resistance that point to be conditioned to receive dial pulses,

in a well-known manner, and as trunk T is a twoway circuit, to make the outgoing terminals of this trunk busy to any switch which may attempt toisei'zeit to originate a call in the opposite direc tion, i. e. toward the toll oirlce' end.

' The toll operator now actuates the dial 24 to transmit the proper impulse code corresponding to the wanted line. When the dial is moved off normal, the upperor oil-normal contacts of the dial are opened thereby releasing relay 15 which thereupon transfers the busy test lead 19 from lead, 3| back to its normal connection to lead 8| and reestablishes the short circuit around resistance 11 thereby removing this resistance from the previously traced pulsing circuit which includes the dial, relay I1, pulsing relay 51 and marginal relay 61 whereupon relay 6'! now operates which in turn operates relay 9| in a circuit traced from battery, contact 63 of relay 54, winding of relay 9|, contact 92 of relay 61 to ground over contact 41 of relay 40. Relay 9| closes an obvious circuit to operate relay 62, which relay opens its contact 93 andcloses contact 94 thereby connecting the tip conductor. 85 of the trunk to the ring conductor 96 through the pulsing contact 91 of relay 51 to the exclusion of the repeating coil 56, upper winding of polarized relay I01 and contact 99 o relay 81.

. The return of the dial interrupts the circuit through relay 51 the required number of times which relay releases and reoperates thereby alternatelyopening and closing the trunk loop to control the switching circuit at the distant ofiice. Relay 61 also follows the interruption of the dial thereby alternately opening and closing the circuit previously traced for relay 9|, but this relay, which is slow' to release, holds operated over these brief open-circuit intervals thereby holding relay 62 operated. Further, due to the closure of contact 98 of relay 62, relay 9| is held operated as long as relay51 is released, under control of relay 54. Whenthe dial restores to normal, relay 7 15 reoperates which again removes the short circuit from resistance 11 thereby again increasing the resistance of the pulsing circuit including marginal relay 61 which latter relay thereupon releases which permits relays 9| and 62 to release in turn.

The release of relay62 opens its contacts 94 and 98 and recloses'contact 93 thereby reconnecting the trunk conductors 95 through the upper right winding of repeating coil 56, upper low resistance winding of relay I01, contact 90 of relay 91, and lower rightwinding of repeating coil 55 to the ring conductor 96. This restores the first digit was dialed.

When the dial is moved 011 normal to transmit the next'digit, the same sequence of operations takes place, and so on, until the dial comes to rest at the conclusion of the dialing operation at which time the operator must release the dial key I in order to free the dial circuit from the trunk and condition the cord for conversation.

When dial key I is released, due to the fact that relay 51 is now operated, ground at the right ground is connected through relay I! to the ring spring of the trunk jack and thence over contact 3! of relay 38 and contact 50 of relay 40 to the lower winding of relay 5| thereby short-circuiting it. During the pulsing period although the pulsing circuit includes the lower winding of relay 5!, and consequently is alternately opened and closed, this relay (5|) remains operated, i. e., while the dial circuit is opened, relay 5| is held operated by its upper winding in a circuit traced from battery, contact 63 of relay 54, lead 64, resistance. I03, upper winding and contacts I04 of relay 5| and contact 89 of relay 54 to ground. When the dial circuit is. closed, thereby operating relay 51, the holding winding of relay 5| is short-circuited in the following path: Ground, contact 86 of relay 51, contact I05 and the upper winding of relay 5|, contact I04 of this relay and contact 89 of relay 54 back to ground.

Ground connected at the junction point I02, by the release of dial key I, is also connected through resistance 11, contact 82 of the dial and contact'23 of relay 5, to lead 3| and thence over the previously traced pulsing circuit including the lower winding of relay 5! and marginal relay GI tacts I06 of relay 5|, now released, upper contacts of relay H3 and upper winding of relay 38 to battery. Operation of relay 38 closes its contacts I2 and II thereby connecting the tip and ring springs of the jack 36 to the respective terminals of the left-hand windings of repeating coil 55. Operation of this relay also opens its contact 48 thereby opening the locking circuit for relay 4| which thereupon releases which in turn opens the circuit for relay 40which also releases. Release of relay 4| opens its contact 85 which up to this time has connected the tip spring of the jack 36 to the lower left-hand terminal of repeating coil 55 which extends to battery through relays 01 and 57.

Relay 38 in operatingalso'closes its contact I08 thereby maintaining a connection between the sleeve of jack 35 and relay 42 and holding this relay operated, which otherwise would have released due to the release of relay 4|.

Further, operation of relay 38 opens its contact 83, thereby removing the short circuit heretofore connected around resistance I09. the closure of contacts I2 and H and opening of contact 83 of relay 38 and the opening of contact 35 of relay 4| is to reverse and reduce the current flowing back into the dial circuit through polarized relay [1 and due to this reversal of currelay I5, contacts 99 and IM of keys I00'an-d I,

The effect of winding of'relay II, lead 32, contact 30 of relay I2, contact I4 of relay I5, contacts of the plug 9, ring spring of jack 36, contact II of relay 38, lower left winding of repeating coil 56, resistance I0, contact 69 of relay 59, lower winding of relay 51, contact 68 of relay 45, winding of relay 61, resistance I09, leads 65 and 64 and contact 63 of relay 54 to the negative pole of battery. Operation of relay II releases relays I8, I9 and I2.

Relay I2 in releasing opens its contacts 29 and 39 thereby disconnecting the dial circuit (leads 3| and 32) from the tip and ring of the trunk, closes its contact 34 to extend the tip of plug 9 to the upper armature of relay I5, opens contacts I6 and closes contacts 35 thereby connecting battery through the cord sleeve relay 33 to the sleeve of plug 9 and consequently to the sleeve of the trunk thereby holding the trunk sleeve relay 42 operated which otherwise would also release.

I Cord'sleeve relay 33 now operates in series with .the trunk sleeve relay 42 thereby operating relay I5. Relay I5 closes through the tip and ring of the cord. Release of relay I8 releases relay i5 and release of relay I9 releases relays 2| and 5 thereby restoring the position dial'circuit (Fig. l) to normal.

With relay I2 released and relay I5 operated the tip and ring conductors of the cord are connected through and the supervisory bridge,

comprising retard coil IIO,and relay II I 'in parallel across the cord, holds relay 5'! operated. Relay III operates at this time and lights supervisory lamp II2.

When the called subscriber answers battery and ground are reversed in the usual manner, over the trunk from the community dial office, causing operation of polarized relay I0! in the trunk.

Operation of relay I01 closes a circuit to operate relay 59 which can be traced over the lower contacts ofrelay 81 and lowermost normal contacts I of relay 40 to battery. Operation of relay 59 opens its contacts 58 and 59 thereby disconnecting the two windings of relay 5I from the previously traced circuit through the cordwhich has held this relay operated and at its upper and lower front contacts substitutes a local holding circuit for relay 51. This, however, opens the circuit for supervisory relay III in the cord which releases and extinguishes the supervisory lamp When the conversation is ended and the called subscriber disconnects, relays I0I and 59 release in turn thereby reconnecting the winding of relay 51 to the cord and reoperating supervisory relay III which lights supervisory lamp IIZ. The toll operator then challenges on the line andfinding the conversation finished removes plug 9 from jack 36 whereupon the trunk circuit restores to normaLwhich operation, as it forms no part of the invention, will not be described in detail.

a What is claimed is: 8

1. In a telephone system, a trunk circuit, an operators cord circuit adapted to be connected to said trunk, a dial adapted to be connected and locked to said cord circuit, a dial key, a polarized relay adapted to be connected inseries with said dial when the dial is connected to the cord, means responsive to the joint connection of said cord circuit to said trunk and operation of saiddial key a to connect said dial to said cord andlock it under control of saidpolarized relay, a source of direct current adapted to be connected to said trunk responsive to the connection of said dial and in a non-operate direction with respect to saidpolarized relay, and means responsive to therelease of said dial key to cause said current source to be reversed in polarity with respect to said trunk to operate said polarized relay and release said dial from the cord. 7

I 2. In a telephone system, an operators cord circuit, a trunk circuit, a dial, a dial key, means responsive to operation of said dial key and cone nection of said cord tothe trunk to 'connectand lock the dial to the cord, a polarized relay in series with the dial controlling the locking circuit automatic exchanges, cord circuits at said manual exchange for making connection to said trunk circuits, a position circuit including an impulse transmitting device and a key at the manual exchange, said device being adapted to be connected and locked to any of said cord circuits jointly responsive to connection of the cord to any one of said trunk circuits and the operation of the key, polarized relay means at said manual exchange in series with said dial when it is connected to a cordadapted when operated to disconnect said dial from its connected cord circuit, means at certain of said automatic exchanges responsive to seizure of the called line thereat to reverse thec'onnection of the exchange battery to the calling trunk circuit to operate said polarized relay means at the manual exchange, and means-associated with said position circuit, cord circuits, and trunk circuits extending to automatic exchanges not arranged to reverse battery to the trunk when the called line is seized, responsive to release of the dial key, to cause direct current to be connected to the trunk circuit at the manual exchange in such a direction, as to operate said polarized relay means to release the dial from its associated cord circuit.

THOMAS H. NEELY. ALBERT G. LANG. 

